We have found that 3-methylfuran is highly toxic to the pulmonary bronchiolar lining cells of experimental animals. Studies are underway to determine whether metabolic activation of this compound to a potent alkylating agent is the biochemical mechanism underlying the pathogenesis of these lesions, as we have shown for several other furano compounds. This finding may be of importance in human respiratory diseases because recent reports have shown that 3-methylfuran is a major air pollutant in cities such as Washington, D.C.